It is often necessary or desirable for a person to exercise a particular muscle or group of muscles. For example, when a muscle is damaged, such as through injury or surgery, it is important to exercise the muscle to prevent atrophy and to strengthen the muscle for normal use. Further, people exercise healthy muscles to increase strength and to maintain an active and healthy lifestyle, as well as to improve their appearance. Various routines have been developed to exercise different muscle groups by forcing the muscles to contract and extend under a load, such as by moving a free weight against the force of gravity or by moving a handle whose movement is resisted by an exercise machine.
One such exercise is known as a chest press. An exerciser lies supine on a bench and grasps a barbell above the exerciser. The exerciser then pushes the barbell upward, away from his chest, and lowers it down. This exercise can be dangerous as the exerciser may drop the barbell. Further, the exerciser should have a partner to spot him in case he fails to lift the weight and becomes trapped below it. Even if done properly with a partner, this exercise may not permit the user a full range of exercise since the barbell may hit the user's chest before the chest and arm muscles have extended fully. When using free weights, the force provided by gravity is constant while the mechanical advantage of the weights on the joints and the strength of the muscles varies over the range of motion. Consequently, the muscles are not fully loaded at each point over the range. During a chest press, the hands seek to follow a curved path inward as the weight is extended from the chest. This path cannot be followed when using a barbell because the hands are maintained at a fixed distance. Alternatively, dumbbells will allow the full range of join motion for the exercise but cannot apply consistent resistance to the joint.
To overcome these difficulties, machines have been developed that simulate the exercise movements of a chest press. In one known apparatus a user exercises by pushing handles away from his chest while in a sitting position. A seat and backrest are mounted to a frame to position a user. Two arms are rotatably mounted as a unit to the frame. The handles are mounted to the arms. The pivot for the arms is disposed above the seat. A cable operably connects the arms to a weight stack such that when a user pushes on the handles, thereby rotating the arms, the weight stack is lifted and provides resistance to the exercise. The cable may extend over a variable radius cam, which alters the distance the weight is displaced for a given amount of handle rotation. In this configuration, the resistance to the movement of the handles can be varied to match the strength curve of the chest muscles. While such an apparatus solves many problems associated with performing a chest press exercise with barbells or dumbbells, it does not permit the user to vary the distance between his hands while performing the exercise.
In another apparatus, disclosed in U.S. Pat. No. 5,044,631, an exercise machine provides levers that are rotatably mounted to a frame above the seated user. Handles are mounted to the levers. Resistance to handle movement is provided by weight plates mounted to the levers. The hinges for the levers are disposed at an angle of 20 degrees with respect to a central vertical midline, such that the user must move his hands in defined arcs in converging planes as he presses forward on the handles. This apparatus forces the user's hands to be brought together at a preset rate as they are pressed away from the chest, regardless of the user's anatomy. This apparatus does not permit the user to select his own path of motion for the press exercise. Rather, the motion is dictated by the angle of the hinges.
An exercise that develops the back muscles is called an incline pull or high row. This exercise involves a pulling motion, wherein a person grips a load with his/her hands, and pulls the load from an arm-extended position to an arms-bent position using primarily the muscles of the back, such as the latissimus dorsi, in addition to ancillary muscles, such as the rear deltoids. The plane of motion is substantially parallel to an imaginary plane bisecting the symmetric halves of the body, such that the arms and elbows are bent and close up against the torso at the end of the motion when the muscles are fully contracted. A “regular” pull or rowing type exercise places the range of motion substantially perpendicular to the longitudinal axis of the torso, and targets the entire range of back muscles. A traditional Lat pull-down range of motion (similar to a pull-up or chin-up) places the range of motion substantially parallel with the major axis of the torso, targeting primarily the latissimus muscles. The “incline pull” is a variation wherein the starting position of the extended arms places the hands at a point above the chest and in front of the head, such that the range of motion is along a path that is angled with respect to both the perpendicular and parallel axes of the torso, allowing for a person to target the muscles in a way that is a mix between the rowing motion and the pull-down motion.
A key variable to the pulling exercise motion is the degree to which the hands are separated and arms are extended away from each other, the so-called “width” of a person's grip. A narrow grip tends to target more of the arm muscles involved in the pulling motion, such as the biceps, and lessens the emphasis on the back muscles. A wider grip puts more emphasis on the back muscles, limiting the range of contraction of the elbows while specifically targeting the latissimus. Known machines provide a range of motion for either a narrow or a wide grip, but do not allow a person to vary the grip during the range of motion.